1. Field of the Invention
The present invention relates to a method of multiple reaction in a microreactor and to the microreactor. More particularly, the present invention relates to a method of multiple reaction in a microreactor and the microreactor capable of obtaining a target product in a high yield by multiple reaction.
2. Description of the Related Art
In recent years, the development of a new manufacturing processing using a microspace called a microreactor has been pursued in the chemical industry or the pharmaceutical industry relating to manufacture of medicines, reagents, etc. A very small space (microreactionchannel) connecting to a plurality of microchannels (fluid introduction channels) is provided in a micromixer or a microreactor. A plurality of fluids (e.g., solutions in which raw materials to be reacted with each other are dissolved) are caused to flow together into the small space. Mixing or mixing and reaction between the fluids are caused thereby. Micromixers and microreactors are basically identical in structure. In some particular cases, however, those in which a plurality of fluids are mixed with each other are referred to as “micromixer”, while those in which mixing of a plurality of solutions is accompanied by chemical reaction between the solutions are referred to as “microreactor”. A microreactor in accordance with the present invention is assumed to comprise a micromixer.
Points of difference between reaction in the a microreactor as defined above and batch mixing or reaction using an agitation tank or the like will be described. That is, chemical reaction in liquid phase occurs ordinarily in such a manner that molecules meet each other at the interface between reaction solutions. In the case of chemical reaction in liquid phase in a very small space, therefore, the area of the interface is relatively increased to such an extent that the reaction efficiency is markedly high. Also, diffusion of molecules itself is such that the diffusion time is proportional to the square of the distance. This means that if the scale of the small space is smaller, mixing progresses faster due to diffusion of molecules to facilitate the reaction, even when the reaction solutions are not positively mixed with each other. Also, in the flow caused in the small space, laminar flows are dominant because of the small scale, and the solutions flow as laminar flows and react with each other by diffusing in a direction perpendicular to the laminar flows.
If such a microreactor is used, the reaction time, mixing temperature and reaction temperature in reaction of solutions can be controlled with improved accuracy in comparison with, for example, a conventional batch system using large-capacity tank or the like as a place for reaction.
Therefore, if multiple reaction is performed by using a microreactor, solutions flow continuously through the small space in the microreactor without staying substantially in the space and a non-uniform reaction product is not easily produced. In this case, a comparatively pure primary product can be extracted.
As such a microreactor, one disclosed in PCT International Publication WO No. 00/62913, one disclosed in Japanese National Publication of International Patent Application No. 2003-502144 and one disclosed in Japanese Patent Application Laid-open No. 2002-282682 are known. In each of these microreactors, two kinds of solutions are respectively passed through microchannels to be introduced into a small space as laminar flows in the form of extremely thin laminations, and are mixed and reacted with each other in the small space.